High intensity discharge lamps utilizing metal vapors as the discharge medium generally require a starting voltage substantially higher than the operating voltage and this is particularly so with high pressure sodium vapor lamps. For such lamps so-called starting aids have become available which are combined with otherwise conventional ballasts to generate a series of high frequency pulses which initiate the breakdown in the lamp.
One very effective starting aid is described in U.S. Pat. No. 3,917,976--Nuckolls, Starting and Operating Circuit for Gaseous Discharge Lamps. It comprises a charging capacitor and a voltage sensitive switch device such as a SIDAC which are connected to form a series discharge loop with a number of turns at the output end of the ballast's reactor or at the output end of the secondary side of the ballast transformer. In addition it comprises a resistor and a high frequency choke coil which are connected in series with the capacitor across the lamp load, that is across the high pressure sodium vapor lamp. Three connections are required to be made from the starting aid into the ballast-lamp circuit, a connection to the high side of the lamp, a connection to a tap near the output end of the ballast, and a connection to the low side of the lamp.
Up to the present one or the other of two approaches have been used with regards to starting aids. One was to attach the components to a flat board or to a printed circuit board and provide additional individual connectors into the ballast-lamp circuit. The other was to encapsulate the components in some suitable material and again provide additional individual connectors into the ballast-lamp circuit. With either of these approaches, the assembly of a starting aid into the lamp ballast circuit in a luminaire or its replacement in the field required mounting the starting aid within the luminaire by means of a suitable bracket and then attaching the individual wires to the terminals of the starting aid. In some situations heat generating components mounted close to the starting aid board have increased the cooling burden and encapsulation on the whole tends to do the same thing. Also with flat board designs, the starting aid needs to be mounted in restricted orientations in order to prevent accumulation of contaminants from causing arcing between live parts.